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When shaft misalignment or motor vibration causes positioning errors in your CNC router or 3D printer, a rigid coupler is often the hidden culprit. Engineers, makers, and machine builders who demand repeatable accuracy rely on flexible jaw couplings to absorb angular and parallel misalignment without transmitting shock loads back to the motor bearings. This flexible plum coupling is engineered for exactly that application.
Each coupler consists of two precision-machined aluminum alloy hubs and a polyurethane spider insert (plum-type jaw). The outer diameter ranges from 20 mm (0.79 in) to 30 mm (1.18 in) and the body length from 25 mm (0.98 in) to 35 mm (1.38 in), with bore pairs spanning 4 mm through 12 mm to accommodate the most common stepper motor shaft and lead-screw combinations.
Typical use cases include Z-axis lead-screw coupling on FDM 3D printers, X/Y ball-screw connections on desktop CNC mills, and servo-to-encoder shaft linking in DIY motion control systems — all scenarios where low backlash and vibration damping directly improve surface finish and dimensional accuracy.
| Coupler Type | Flexible jaw / plum coupling |
|---|---|
| Hub Material | Aluminum alloy (anodized) |
| Spider Insert Material | Polyurethane (PU) |
| Outer Diameter (OD) | 20 mm / 25 mm / 30 mm (see variant options) |
| Body Length (L) | 25 mm / 30 mm / 35 mm (see variant options) |
| Bore Diameter (each end) | 4 – 12 mm (see variant options) |
| Bore Combination | See variant options |
| Fastening Method | Set screw clamp |
| Finish | Natural anodized aluminum |
| Max Torque | See variant options |
| Weight | See variant options |
Match the bore diameters to your motor shaft and lead-screw shaft diameters. For example, a NEMA 17 motor typically has a 5 mm shaft, so you would select a bore pair such as 5×5 or 5×8 depending on your lead-screw diameter. Then choose the OD and length that fit within your motor mount clearance — D20mm × L25mm is the most compact option.
A rigid coupler transmits torque with zero flex, which means any shaft misalignment creates side-loading on motor bearings and can cause premature failure. This flexible plum coupler uses a polyurethane spider insert to accommodate angular and parallel misalignment (typically up to 1° angular and 0.2 mm parallel), protecting bearings while still delivering low-backlash torque transmission.
Yes. 6.35 mm is the metric equivalent of ¼ inch (0.250 in), so the 6.35×6.35 bore variant is directly compatible with standard ¼-inch imperial motor shafts and lead screws commonly found in North American CNC kits.
Yes. NEMA 17 motors typically use 5 mm shafts and NEMA 23 motors commonly use 6.35 mm or 8 mm shafts. This product range covers bore pairs from 4 mm to 12 mm, so you can find a matching variant for both motor frame sizes. Check your motor datasheet for the exact shaft diameter before ordering.
The split-hub clamp design with set screws provides a secure mechanical grip on the shaft. For best results, ensure the shaft surface is clean and free of oil before tightening the set screws to the recommended torque. The aluminum hubs are machined to close bore tolerances to minimize play before clamping.
The aluminum hubs are anodized, which provides a degree of corrosion resistance suitable for typical indoor workshop and enclosed CNC environments. For prolonged exposure to moisture, condensation, or outdoor conditions, we recommend applying a light protective coating or selecting a stainless-steel coupler variant if available.
Yes — that is one of the key advantages of this product. Each hub is bored independently, so variants like 4×10, 5×8, 6×8, and 5×12 allow you to connect a smaller motor shaft to a larger lead-screw shaft without any adapter sleeves or custom machining.
